Ultra high-sensitive, prompt response and recovering Pt/(Pt+SiO₂) cermet layer/GaN-based hydrogen sensor for...

In this work, we report an ultra-high sensitive (S = 1.4 × 10⁸%), prompt response and recovering Pt/Pt+SiO₂cermet layer/GaN-based hydrogen (H₂) sensor. A sensor fabricated with a 15 nm cermet layer, comprising Pt and SiO₂, deposited between 15 nm Pt and GaN layers, exhibits significantly enhanced sensitivity in the detection of 4 %H₂by ≈ 300×, as compared to the reference Pt/GaN sensor at ambient temperature (300 K). Furthermore, the sensitivity of the our sensor shows very weak dependence on temperature (T) with maximum sensitivity (Smax) reducing from 1.4 × 10⁸% to 2.3 × 10⁷% as temperature increases from 300 to 423 K. The shift in the threshold voltage of the test sensor (ΔV_t,test= 767 mV) increases by 50 % as compared to the shift in threshold voltage of the control sensor (ΔV_t,control= 511 mV) at 1 mA/cm². In addition, the cermet sensor also demonstrates fast response/recovery time, which reduces from 4.58 (2.36) seconds to 94 (39) milliseconds as the temperature increases from300to 423 K. The maximum sensitivity (Smax), response (τ_a) and recovery (τ_b) times of the test sensor when exposed to 10 000 ppm of H₂are 3.9 × 10⁷%, 30 secs and 30.1 secs respectively. The shift in the threshold voltage of the test sensor at 1 mA/cm²when exposed to 100 ppm, 1000 ppm, 5000 ppm, and 10 000 ppm are 40 mV, 70 mV, 460 mV, and 600 mV, respectively. The 2-Dimensional (2D) trapping of H-atoms by the oxygen atoms present in the Pt+SiO₂cermet layer and porous/compact layer models explains the underlying mechanism, which results in a significant improvement of the sensing characteristics of the test sensor. The Thermionic Emission (TE) model effectively models the current density (J) - voltage (V) characteristics of both control and test sensors, with and without hydrogen. The prompt detection of high percentages of hydrogen in life-saving and commercial fuel applications becomes possible with the Pt+SiO₂cermet-based sensor, with its response and recovery times in the order of milliseconds for a temperature range of 363-423 K.